The present invention relates to a colour sorting apparatus for granular objects, and more particularly, to a colour sorting apparatus in which the background brightness is automatically controlled to be at an appropriate level while in operation.
A conventional colour sorting apparatus, with which acceptable and unacceptable granular objects or grains are sorted by their colour, has a disadvantage in that it is necessary to interrupt the sorting operation to adjust the background brightness to an appropriate level every time the tone of colour of the acceptable objects changes, and therefore, it takes time for the adjusting operation particularly in a colour sorting apparatus having a plurality of sorting units arranged in a horizontal row, thereby seriously deteriorating the sorting efficiency.
One object of the present invention is therefore to eliminate the disadvantage of the conventional colour sorting apparatus for granular objects.
Another object of the present invention is to provide a colour sorting apparatus for granular objects in which the background brightness is automatically adjusted according to the changes of the tone of colour of the acceptable objects while in operation.
Still another object of the present invention is to provide a colour sorting apparatus for granular objects in which the difference in the amount of light received by a light receiving element in the case where acceptable objects exist in a sorting path in a sorting chamber and in the case where no object exists in the sorting path is automatically controlled to be substantially zero while in operation, so as to make it possible to perform the sorting operation with high efficiency, thereby attaining high volume production of finely selected granular objects.
Still another object of the present invention is to provide a colour sorting apparatus having a plurality of sorting units arranged in a horizontal row in which the automatic adjustment of the background brightness can be successively performed over a plurality of colour sorting units.